Show metadata for rendered images

Previously metadata was only shown for images which are saved
to disk.

This change makes it so that it's possible to see metadata right
after pressing F12.

source/blender/blenkernel/intern/image.c

@@ -3958,6 +3958,15 @@ static ImBuf *image_get_render_result(Image *ima, ImageUser *iuser, void **r_loc
 		ibuf->flags &= ~IB_zbuffloat;
 	}
 
+	/* TODO(sergey): Make this faster by either simply referencing the stamp
+	 * or by changing both ImBug and RenderResult to use same data type to
+	 * store metadata. */
+	if (ibuf->metadata != NULL) {
+		IMB_metadata_free(ibuf->metadata);
+		ibuf->metadata = NULL;
+	}
+	BKE_imbuf_stamp_info(&rres, ibuf);
+
 	BLI_thread_unlock(LOCK_COLORMANAGE);
 
 	ibuf->dither = dither;